Black carbon

Black carbon, a component of soot, is a potent climate-forcing aerosol and may be the second leading cause of global warming after carbon dioxide (CO2). Unlike CO2, however, black carbon remains in the atmosphere for only a few days or weeks. Therefore reducing these emissions will have an almost immediate climate mitigation impact. While substantial reductions of greenhouse gas emissions should remain the anchor of overall climate stabilization efforts, dealing with black carbon may be the fastest means of near-term climate mitigation and could be critical in forestalling climate tipping points.

Black carbon is a product of the incomplete combustion of fossil fuels, biofuels, and biomass. The main sources are open burning of biomass, diesel engines, and the residential burning of solid fuels such as coal, wood, dung, and agricultural residues. Black carbon contributes to climate change in two ways: It warms the atmosphere directly by absorbing solar radiation and converting it to heat and indirectly by darkening the surfaces of ice and snow when deposited on them. This reduces albedo, the ability to reflect light, and thereby increases heat absorption and accelerates melting. As large masses of both land and sea ice disappear, they reflect less and less solar radiation, so heat is increasingly absorbed at the surface. Thus not only do sea and land ice face tipping points of irreversible melting, but this melting can create positive feedbacks leading to even further warming.

"The emerging link between black carbon and climate change" (22 June 2010). Hosted by The Parliament magazine at the European Parliament. A summary of the event is available here, or watch the short video clip below.